Sensor system and method

ABSTRACT

A sensing system includes a conductor with a current flow path therethrough. A first location of the conductor defines a first cross-sectional area and a second location defines a second cross-sectional area, wherein a current flowing through the conductor establishes magnetic field lines having strengths that vary according the conductor cross-sectional area. A plurality of sensors include a first and second sensors situated proximate the first and second locations, respectively, and configured to measure the magnetic field lines at their respective locations.

BACKGROUND

Sensors for detecting current flow through a conductor are known. Tosense and measure the current flow, the sensors measure the magneticfield generated by the current flowing through a conductor. To achievethe desired measurements, multiple sensors with different sensitivitiesare often used with such known devices. Further, to adjust thesensitivity, magnetic circuits consisting of soft magnetic materials areused to modify the magnetic field strength. However, multiple sensorsand/or additional magnetic materials add cost and require additionalspace. Further, they can cause hysteresis, remanence, temperature drift,non-linearity, reduced bandwidth, etc.

For these and other reasons, there is a need for the present invention.

SUMMARY

A magnetic sensing system and corresponding methods are disclosed. Thesensing system includes a conductor with a current flow path. A firstlocation of the conductor defines a first cross-sectional area and asecond location defines a second cross-sectional area, wherein a currentflowing through the conductor establishes magnetic field lines havingstrengths that vary according the conductor cross-sectional area. Aplurality of sensors include a first sensor situated proximate the firstlocation and a second sensor located proximate the second location. Thesensors are configured to measure the magnetic field lines at theirrespective locations.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the present invention and are incorporated in andconstitute a part of this specification. The drawings illustrate theembodiments of the present invention and together with the descriptionserve to explain the principles of the invention. Other embodiments ofthe present invention and many of the intended advantages of the presentinvention will be readily appreciated as they become better understoodby reference to the following detailed description. The elements of thedrawings are not necessarily to scale relative to each other. Likereference numerals designate corresponding similar parts.

FIG. 1 is a perspective view illustrating a current sensor including anembodiment of a conductor as disclosed herein.

FIG. 2 illustrates an embodiment of the conductor illustrated in FIG. 1made of several parts.

FIG. 3 is a top view of the embodiment illustrated in FIG. 1.

FIG. 4 is a schematic diagram of a wheatstone bridge.

FIG. 5 illustrates a simulated magnetic field that would be generated bythe embodiment of the conductor illustrated in FIG. 1.

FIG. 6 illustrates a current sensor including an embodiment of aconductor as disclosed herein.

FIG. 7 illustrates a current sensor including another embodiment of aconductor as disclosed herein.

FIG. 8 illustrates a simulated magnetic field that would be generated bythe embodiment of the conductor illustrated in FIG. 7.

FIG. 9 illustrates a current sensor including an embodiment of aconductor as disclosed herein using a U-shaped.

FIGS. 10A-10E illustrate embodiments of conductors as disclosed hereinusing a U-shaped and folded geometry.

FIGS. 11A-11D illustrate a current sensor including another embodimentof a conductor as disclosed herein.

FIG. 12 illustrates a current sensor including another embodiment of aconductor as disclosed herein.

FIGS. 13A and 13B illustrate a current sensor including anotherembodiment of a conductor as disclosed herein.

FIGS. 14A and 14B illustrate a current sensor including anotherembodiment of a conductor as disclosed herein.

FIG. 15 illustrates a current sensor including another embodiment of aconductor as disclosed herein.

FIGS. 16A and 16B illustrate a current sensor including anotherembodiment of a conductor as disclosed herein.

FIG. 17 illustrates a simulated magnetic field that would be generatedby the embodiment of the conductor illustrated in FIG. 16.

DETAILED DESCRIPTION

In the following Detailed Description, reference is made to theaccompanying drawings, which form a part hereof, and in which is shownby way of illustration specific embodiments in which the invention maybe practiced. In this regard, directional terminology, such as “top,”“bottom,” “front,” “back,” “leading,” “trailing,” etc., is used withreference to the orientation of the Figure(s) being described. Becausecomponents of embodiments of the present invention can be positioned ina number of different orientations, the directional terminology is usedfor purposes of illustration and is in no way limiting. It is to beunderstood that other embodiments may be utilized and structural orlogical changes may be made without departing from the scope of thepresent invention. The following detailed description, therefore, is notto be taken in a limiting sense, and the scope of the present inventionis defined by the appended claims.

A current sensing system is disclosed in which, instead of influencing amagnetic field to be measured by permeable materials, particularconductor geometries are provided to generate an inhomogeneous field.Two or more magnetic sensors are placed at positions with differentfield intensities, resulting in a change in the sensitivity of thesensor and increasing dynamic range. The signals of the sensors can besimply added (by a series connection) or combined by analog or digitalsignal processing. In addition, sensor elements with differentsensitivities can be used in order to further enhance the dynamic range.Thus, an inhomogeneous gradient magnetic field generated by currentconductors is used to realize current sensors with a high dynamic range.

FIG. 1 illustrates an embodiment of a magnetic sensing system 100. Aconductor 110 includes a current input end 112 and a current output end114, which defines a current flow path 116 from the current input end112 to the output end 114. Aluminium or copper, for example, aresuitable materials for the conductor 110. The conductor 110 has avarying cross section, such that for example, one location 120 has afirst cross-sectional area and another location 122 has a larger secondcross-sectional area. In the embodiment illustrated in FIG. 1, thevarying cross sectional area results from an opening, such as a notch124 formed in the conductor 110. Thus, a current flowing through theconductor 110 establishes magnetic field lines having strengths thatvary due to the varying cross-sectional area of the conductor, resultingin an inhomogeneous magnetic field.

The conductor 110 illustrated can be constructed using multiple parts,as illustrated in FIG. 2, which uses three components 110 a, 110 b and110 c that can be formed by a standard stamping process. The particulardimensions of the conductor 110 will vary depending on the application.Typical height h and width w dimensions in some embodiments are about 5mm and about 8 mm, respectively.

A plurality of sensors 130 are situated proximate locations of thesensor having different cross-sectional areas, such as the locations 120and 122. The sensors 130 are configured to measure the magnetic fieldlines of the inhomogeneous field at their respective locations. Thesensors 130 typically are mounted to a substrate and packaged, resultingin a sensor package 132. In the embodiment illustrated in FIG. 2, thechip package 132 can be placed between components forming the conductor110. In some embodiments, the middle component 110 b is a leadframe fora sensor chip, in which case an insulator is situated between each ofthe components 110 a, 110 b, 110 c.

FIG. 3 illustrates sensor placements used in example embodiments. InFIG. 3, four sensors 130 a and 130 b are illustrated. However, sincedifferential measurements are typically used, each of the ovalsrepresenting the sensors 130 is actually a pair of sensors, wherecorresponding pairs of sensors, such as the sensors 130 a, form the legsof a bridge circuit such as in the example wheatstone bridge circuitillustrated in FIG. 4. In the embodiment shown in FIG. 3, some of thesensors are situated in the notch, with the sensors 130 a at the lowerportion of FIG. 3 covered by the conductor 110, while the sensors at theupper part of the drawing (both sensors 130 b and the upper sensor 130)have at least a portion of the sensor exposed.

The sensors 130 are situated in predetermined positions to provide ahigh dynamic range. In FIG. 3, the sensors 130 are situated on a line134. FIG. 5 illustrates a simulated magnetic field 140 generated alongthe line 134 in the plane of the sensor package 132. The two pairs ofsensors 130 a are situated at high sensitivity locations. Morespecifically, in the illustrated embodiment, the sensors 130 a arepositioned at the locations of the minimum (negative peak) and maximum(positive peak) value of the magnetic field lines (towards the outeredges of the conductor 130). The other pairs of sensors 130 b aresituated at low sensitivity locations—between the first sensors 130 a,such that the sensors 130 b are in positions where the value of themagnetic field lines is greater than the minimum and less than themaximum. Further, the corresponding sensor pairs of each of the sets ofsensors 130 a, 130 b are approximately equidistant from thezero-crossing point of the magnetic field lines. The exact positions ofthe sensors 130 b depends on the particular application. Generally, thestrength of the magnetic field (absolute value) at the high sensitivitypositions (sensors 130 a) is at least twice the value of the magneticfield at the location of the low sensitivity positions (sensors 130 b).In some embodiments, the strength of the magnetic fields at the high andlow sensitivity positions differs by a factor of 10.

FIGS. 6 and 7 illustrate further embodiments, where the conductor 110has a decreasing cross-sectional area from left to right as viewed inthe drawings. In both FIGS. 6 and 7, the conductor 110 is a prism with agenerally square or rectangular cross-section. In FIG. 6, thecross-sectional area continuously decreases, and in FIG. 7, thecross-sectional area decreases in a stepped fashion. In both FIGS. 6 and7, the sensor package 132 is situated next to the conductor 110, withthe individual sensor pairs 130 positioned at locations of varyingcross-sectional areas of the conductor 110. The magnetic field detectedby the sensors 130 increases with decreasing conductor cross-sectionalarea. FIG. 8 illustrates a simulated magnetic field 140 for theconductor 110 shown in FIG. 7. Additionally, the sensitivities of thesingle sensors 130 can be varied along the portion of the conductor 130having the varying cross-sectional area. For example, when a highsensitivity sensor is used where the magnetic field is high, and a lowsensitivity sensor is used where the magnetic field is low, the wholedynamic range of the sensor system is increased.

In embodiments where differential measurements are desired, a U-shapedconductor 130 is used. FIG. 9 illustrates an embodiment where two legs136 similarly shaped to the conductor 130 illustrated in FIG. 7 areconnected to a U-shaped central portion 138. Thus, the current input 112and output 114 are at the same end of the conductor 110. A sensorpackage 132 is positioned next to the legs 136 with sensors 130 situatedto sense the magnetic field.

FIGS. 10A-10E illustrate additional U-shaped embodiments, where a foldedconstruction is used. The folded geometry generates a higher maximumfield and a higher gradient. FIG. 10A illustrates a top view of aU-shaped embodiment that includes portions having a decreasingcross-sectional area similar to the embodiment illustrated in FIG. 6.FIG. 10A illustrates an embodiment prior to folding the conductor 130.The U-shaped end 138 is folded over the legs 136 of the conductor 110.FIG. 10B illustrates a side view and FIG. 10C is a top view afterfolding the 110 of FIG. 10A. FIGS. 10D and 10E illustrate a foldedembodiment with additional conductor legs 160 connecting the top andbottom sections of the folded conductor 130.

FIGS. 11A-11D illustrate another embodiment of the conductor 110 havingan opening extending through the conductor. FIG. 11A is a perspectiveview, FIG. 11B is a front view, FIG. 11C is a cross-sectional side viewand 11D is a cross sectional top view illustrating placement of sensors130 a and 130 b used in an embodiment. As with the embodimentillustrated in FIG. 1, the conductor 110 illustrated in FIG. 11 includesa current input end 112 and a current output end 114 with an opening 124extending through the conductor 110. FIG. 11D illustrates the currentflow direction 150 on either side of the opening 124 (current flowinginto the drawing sheet in FIG. 11D), establishing a magnetic fieldhaving a varying strength due to the varying cross-sectional area of theconductor 110 resulting in an inhomogeneous magnetic field.

FIG. 12 illustrates an embodiment similar to that shown in FIG. 11,where the opening 124 has a different shape. The embodiment illustratedin FIG. 12 has a similar cross section to the view of FIG. 11D, and canhave similar placement of the sensors 130 a and 130 b. FIGS. 13 and 14illustrate additional embodiments having different configurations of theopening 124. FIGS. 13B and 14B illustrate cross-sectional views takenthrough the openings 124 of the respective embodiments illustrated inFIGS. 13A and 13B. FIGS. 13B and 14B illustrate example positioning ofthe sensors 130 a and 130 b.

FIGS. 15 and 16 illustrate embodiments having further conductorgeometries. The embodiments illustrated in FIGS. 15 and 16 have openings124 therein, and also define locations having different cross sectionalareas. FIG. 17 illustrates a simulated magnetic field 140 for theembodiment illustrated in FIG. 16. As with other disclosed embodiments,the sensors 130 a are positioned at high sensitivity areas, where themagnetic field is at the negative and positive peaks. FIG. 16A is across-sectional view of the conductor 110 illustrated in FIG. 16A,illustrating placement of the sensors 130 a and 130 b within the opening124. In the configuration of FIG. 16, the portion of the curve 140 nearthe center is fairly flat and nearly linear. Thus, the positioning ofthe sensors 130 b is not particularly critical. The positioning of thesensors 130 a, however, needs to be more precise. Since the value of themagnetic field is high, errors in positioning the sensors 130 a canresult in more influence on a system employing the conductor 110.

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat a variety of alternate and/or equivalent implementations may besubstituted for the specific embodiments shown and described withoutdeparting from the scope of the present invention. This application isintended to cover any adaptations or variations of the specificembodiments discussed herein. Therefore, it is intended that thisinvention be limited only by the claims and the equivalents thereof.

1. A magnetic sensing system, comprising: a conductor having a current flow path; the conductor having a first location defining a first cross-sectional area and a second location defining a second cross-sectional area, wherein a current flowing through the conductor establishes magnetic field lines having strengths that vary according to the conductor cross-sectional area; and a plurality of sensors including a first sensor situated proximate the first location and a second sensor situated proximate the second location, the sensors being configured to measure the magnetic field lines at their respective locations; wherein the sensors are arranged in respective pairs that form legs of a bridge circuit and wherein a first one of the pairs of sensors is situated at a location where the value of the magnetic field lines is at a maximum; a second one of the pairs of sensors is situated at a location where the value of the magnetic field lines is at a minimum; and third and fourth ones of the pairs of sensors are situated at locations where the value of the magnetic field lines are greater than the minimum and less than the maximum, and the third and fourth ones of the pairs of sensors are situated at locations approximately equidistant from a location where the magnetic field lines are zero.
 2. The magnetic sensing system of claim 1, wherein the conductor has an opening therein, and wherein at least one of the sensors are situated in the opening.
 3. The magnetic sensing system of claim 2, wherein the sensor situated in the opening has at least one side not covered by the conductor.
 4. The magnetic sensing system of claim 1, wherein the conductor has a section with a continuously decreasing cross-sectional area.
 5. The magnetic sensing system of claim 1, wherein the conductor has a section where the cross-sectional area decreases in a stepped fashion.
 6. The magnetic sensing system of claim 1, wherein the conductor is generally U-shaped.
 7. The magnetic sensing system of claim 1, wherein the sensors are situated on a common plane.
 8. The magnetic sensing system of claim 1, wherein the sensors are mounted to a substrate.
 9. A method of producing a magnetic sensor, comprising: forming a conductor having a first cross-sectional area and a second cross-sectional area; placing first and second pairs of sensors at first and second locations where the value of the magnetic field lines are at a maximum and a minimum, respectively; connecting the first and second pairs of sensors in a first bridge configuration; placing third and fourth pairs of sensors at third and fourth locations where the value of the magnetic field lines are greater than the minimum and less than the maximum, wherein the third and fourth locations are approximately equidistant from a location where the magnetic field lines are zero; and connecting the third and fourth pairs of sensors in a second bridge configuration.
 10. The method of claim 9, further comprising forming an opening in the conductor and placing at least some of the first and second pairs of sensors in the opening.
 11. The method of claim 9, wherein forming the conductor includes folding the conductor.
 12. The method of claim 9, further comprising placing the sensors on a common plane.
 13. A magnetic sensing method, comprising: applying a current to a conductor; providing a plurality of sensors arranged in first, second, third and fourth pairs that form legs of a bridge circuit; situating the first and second pairs at first and second locations to measure magnetic field lines of an inhomogeneous magnetic field at the first and second locations where the value of the magnetic field lines are at a maximum and a minimum, respectively; and situating the third and fourth pairs at third and fourth locations to measure magnetic field lines at the third and fourth locations where the value of the magnetic field lines are greater than the minimum and less than the maximum, wherein the third and fourth locations are approximately equidistant from a location where the magnetic field lines are zero.
 14. The magnetic sensing method of claim 13, wherein the conductor has an opening therein, and wherein the magnetic field lines are measured at a location proximate the opening.
 15. A magnetic sensing system, comprising: a conductor having a current flow path; the conductor having a first location defining a first cross-sectional area and a second location defining a second cross-sectional area, wherein a current flowing through the conductor establishes magnetic field lines having strengths that vary according the conductor cross-sectional area; and means for measuring magnetic field lines of an inhomogeneous magnetic field established in the conductor at first and second locations where the value of the magnetic field lines are at a maximum and a minimum, respectively; and at third and fourth locations where the value of the magnetic field lines are greater than the minimum and less than the maximum, wherein the third and fourth locations are approximately equidistant from a location where the magnetic field lines are zero.
 16. The magnetic sensing system of claim 15, wherein the conductor has an opening therein.
 17. The magnetic sensing system of claim 15, wherein the conductor has a section with a continuously decreasing cross-sectional area.
 18. The magnetic sensing system of claim 15, wherein the conductor has a section where the cross-sectional area decreases in a stepped fashion.
 19. The magnetic sensing system of claim 15, wherein the conductor is generally U-shaped. 